Tax liability for guardians and trustees: they stand liable for tax, interest and penalty as if the incapacitated person were capacitated. Where a business liable to tax is conducted by a guardian, trustee or agent for a minor or other incapacitated person, the guardian, trustee or agent is liable for the tax, interest and penalty in the same manner and to the same extent as the minor or incapacitated person would be if capacitated and conducting the business personally, and the Act's provisions apply accordingly.